Text Messaging to Increase Physical Activity

The
objective of this two-week program is to use text messaging as a strategy to
increase physical activity among adolescents. An experimental evaluation found
that text messages targeting affective beliefs (enjoyable/unenjoyable) increased
the physical activity of inactive adolescents. The intervention had no impact on
active adolescents. Instrumental text messages and affective/instrumental
combined text messages had no impact on any adolescents’ physical activity.

DESCRIPTION OF PROGRAM

Target
population:
Adolescents.

The
program aims to increase physical activity levels by sending adolescents one
text message per day over a period of two weeks. The text messages are
structured this way: “Physical activity can (make you feel)…What activity will
you do today?” There are three treatment conditions in terms of the content of
the text messages: 1) affective beliefs (“cheerful,” “inspired,” “proud”); 2)
instrumental beliefs (“maintain healthy weight,” “increase energy levels,”
“avoid illness”); or 3) a combination of these (half affective, half
instrumental).

Evaluated population: A total of 128 adolescents ages 16-19 years participated in the evaluation at
baseline. The adolescents were recruited from four “sixth form” schools. Each
adolescent had a mobile phone, and 70 percent were female.

Approach:
Adolescents in this pilot study were randomly assigned to one of three
experimental conditions, 1) affective beliefs (N = 31), 2) instrumental beliefs
( N = 30), or 3) a combination of these (N = 31), or the control condition (N =
28). Adolescents in the control condition received one text message per week
(“What activity will you do today?”) Adolescents were randomized using a random
number generator, and stratified so that there was an equal distribution of
participants in each of the four conditions (3 treatment and 1 control) in each
school. Physical activity was assessed via adolescent self-report at baseline
and at the end of the two-week intervention. There was no adjustment for
clustering. The different treatment and control conditions were equivalent at
baseline in terms of initial activity levels, gender, and school. Eight
adolescents were lost to follow-up.

Results:
Among
participants who were inactive at baseline (but not those who were active at
baseline), those who received the affective text messages increased their
physical activity significantly more than those who received the instrumental,
combined, and control text messages. There were no differences in physical
activity between the instrumental, combined, and control text message groups.

A
potential limitation is that no long-term data were collected in this pilot
study, and it seems possible that participants reported higher levels of
physical activity due to social desirability.